U.V. Sterilizers for the Pond

by Richard Renshaw
Ventura County Koi Society

One of the fastest growing products for a Koi pond is the ultra-violet (U.V.) sterilizer. The ultra-violet sterilizer is a device which uses U.V. light to kill micro-organisms in water. U.V. light bulbs look like a fluorescent light bulbs. Ultra-violet disinfection has been used for many years in hospitals and in water purification. There are even units made for sanitizing spa and hot tubs. The aquarium hobbyists have U.V. sterilizers available for delicate aquarium setups. The Koi hobby has known about U.V. for over 10 years, but have not accepted the technology until now. The reason is, there is some confusion as to what to expect. A U.V. unit is not meant to replace a bio-filter. You still need a bio-filter for removing the ammonia wastes. You should not expect the U.V. unit to sterilize your pond. There will be bacteria on and in your fish, in the biological filter bed, and on the walls and bottom of the pond. What you can expect is to control harmful bacteria, algae, and other waterborne microorganisms by reducing their numbers. The trick is not to destroy all the organisms in one cycle. But, to expose the unwanted organisms to repeated small doses over a period of time. With this in mind, you will need a 500 - 1500 GPH flow rate for a 15 - 50 watt U.V. unit. If your flow rate is greater, you can install a "tee" before the U.V. sterilizer and bypass the excess flow around the unit. When using a "tee", have the main flow directed straight into the U.V. unit and the bypass coming off the existing straight pipe. That way you will get maximum flow through the U.V. unit. Since some of the U.V. sterilizers are designed for other applications, it is important to know what to look for:

In conclusion, U.V. sterilizers do work, but they are expensive. Be aware of poorly designed equipment. Usually a normal sterilizer unit looks like a 3 inch white pvc pipe with inlet/outlet connections on the side at each end and a U.V. tube running through the center. The ends of the tube (U.V. bulb) will be sealed with o-rings and the wiring connections covered with rubber boots. If ultraviolet sterilizers sound interesting, and you are looking for a source for good pond quality U.V. units:

Aqua Art (more information on U.V.)
1341 Money Way
St. Helena, CA 94574
e-mail: aquaart@napanet.net

Aquanetics
5252 Lovelock St.
San Diego, CA 92110

Aqua Ultraviolet
43339 Business Park Dr. Ste 103
Temecula, CA 92590
For location of a dealer: 1-800-454-2725

The Tropical Marine Centre Ltd
Solesbridge Lane, Chorleywood
Rickmansworth, Herts. WD3 5SX
Tel: 09278 4151

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Copyright © 1996, Richard Renshaw, Revised March 15, 1997